The present invention relates to a device for expanding a pipe, such as a casing string or a liner in a borehole.
Pipe expansion is done to increase the diameter of a pipe, this is particular relevant to a well completion, wherein a number of casing strings is introduced into a borehole to protect the borehole from collapsing and to contain the well fluids therein. In such a completion each next casing string has a smaller diameter than the preceding one, in order that the next casing string can be put in place. Consequently the cross-section available to fluid flow through the completion becomes smaller and smaller as the number of casing strings increases. And this adversely affects the production from the well. To overcome this the casing strings are expanded so that the overall internal diameter of the well completion is not reduced.
Pipe expansion is achieved by displacing through the pipe an expansion device having a larger diameter than the inner diameter of the pipe. Because the forces exerted on the expansion device during pipe expansion are large, such expansion devices have fixed dimensions. And this implies that the expansion has to be performed in stages.
It is an object of the present invention to provide a device for expanding a pipe to the same diameter as the pipe through which the pipe to be expanded is run. It is a further object of the present invention to provide a device of which outer diameter can easily be adjusted, and that is sufficiently strong to withstand the forces that it subjected to during the pipe expansion.
To this end the device for expanding a pipe according to the present invention comprises a bi-conical sleeve having a first section widening from one end of the bi-conical sleeve to the middle and a second section widening from the opposite end of the bi-conical sleeve to the middle, which sections are provided with at least two longitudinal guide channels which guide channels in the second section are staggered in relation to the guide channels in the first section, a set of first wedges, wherein each first wedge tapers into the direction in which the first section widens and is provided with a support element that co-operates with the corresponding longitudinal guide channel of the first section, a set of second wedges, wherein each second wedge tapers into the direction in which the second section widens and is provided with a support element that co-operates with the corresponding longitudinal guide channel of the second section, and means for moving the sets of wedges into each other.